Bug 1385478 - Part 1: Use IsRequired/Required() to get the current required state. r=bz

IsRequired() helper function returns the current 'required' state of the
element, that is, whether its required attribute is set or not. This will be
used only for input elements that @required applies.

dom/html/HTMLTextAreaElement.cpp

@@ -958,7 +958,7 @@ HTMLTextAreaElement::IntrinsicState() const
 {
   EventStates state = nsGenericHTMLFormElementWithState::IntrinsicState();
 
-  if (HasAttr(kNameSpaceID_None, nsGkAtoms::required)) {
+  if (Required()) {
     state |= NS_EVENT_STATE_REQUIRED;
   } else {
     state |= NS_EVENT_STATE_OPTIONAL;
@@ -1218,7 +1218,7 @@ HTMLTextAreaElement::IsTooShort()
 bool
 HTMLTextAreaElement::IsValueMissing() const
 {
-  if (!HasAttr(kNameSpaceID_None, nsGkAtoms::required) || !IsMutable()) {
+  if (!Required() || !IsMutable()) {
     return false;
   }